SAPO-34分子筛晶种辅助合成SSZ-13分子筛

在水热合成体系中,对以SAPO-34作为异质晶种制得纯相SSZ-13分子筛的合成条件进行了考察,并与SSZ-13为晶种的合成产物进行对比研究,同时考察了其甲醇制烯烃(MTO)反应性能。结果表明,适量SAPO-34分子筛的加入可对SSZ-13分子筛的合成起到辅助晶化的作用,有效抑制杂晶并提高产物结晶度,已焙烧或结晶度较低的SAPO-34分子筛的辅助晶化效果更明显。以SAPO-34异质晶种与SSZ-13同质晶种合成的SSZ-13产物相比,具有相似的物化性质、酸性质以及催化性能,由此说明SAPO-34可以替代SSZ-13作为SSZ-13分子筛的合成晶种。     

One-pot synthesis of hierarchically nanoporous SSZ-13 for conversion of methanol-to-olefins

The main disadvantage of microporous SSZ-13 catalyst used in the methanol to olefins(MTO) process is its rapid deactivation due to its relatively low coke resistance. Meanwhile, the hierarchical zeolites usually exhibit improved catalytic stability thanks to their better mass transfer ability. Herein, the hierarchically nanoporous SSZ-13 zeolites were one-pot synthesized by using N,N,N-trimethyl-1-adamantanammonium hydroxide as a microporous structure directing agent and C_(18)H_(37) N~+(CH_3)_2 C_6H_(12) N~+(CH_3)_2 C_6 H_(13)(Br~-)_2(hereinafter abbreviated as C_(18-6-6) Br_2) as a mesoporogen. The hierarchically nanoporous SSZ-13 catalyst was characterized by XRD, N_2 physisorption, SEM, TEM, TG-DTG, ~(27) Al and ~(29) SiNMR spectroscopy and NH_3-TPD techniques. The results showed that the hierarchical SSZ-13 zeolite synthesized in the presence of the C_(18-6-6) Br_2 surfactant exhibits aggregates of primary nanocrystals and contains the well-developed mesopores and excellent acidity. Compared to its conventional counterpart, the hierarchical SSZ-13 zeolite has longer catalytic lifetime and higher selectivity for ethylene and propylene in the MTO reaction, which can be attributed to the synergistic effect of their good acidity and improved diffusion properties resulted from the hierarchical pore structure.     

ZSM-5/SAPO-34复合分子筛的合成及甲醇制烯烃催化性能

将预处理的ZSM-5分子筛加入到SAPO-34分子筛的合成混合物中,合成了ZSM-5/SAPO-34双微孔复合分子筛。采用XRD、SEM、FT-IR、NH3-TPD对其结构及物化性能进行了表征,并以甲醇制烯烃(MTO)反应对其催化性能进行了评价。结果表明,以该复合分子筛为催化剂时,甲醇转化率可以长时间维持近100%水平,其催化稳定性远远高于SAPO-34分子筛;与ZSM-5分子筛和相应的机械混合样品相比,具有更高的乙烯、丙烯选择性。因此,ZSM-5/SAPO-34复合分子筛有可能是一种适宜的MTO反应催化剂。